Method and apparatus for protecting a substrate surface from contamination using the photophoretic effect

Abstract

An apparatus for processing a substrate surface in a process chamber wherein during chemical or physical altering of the substrate surface a laser beam is projected inside the processing chamber and along a trajectory which does not contact the substrate surface in order to capture particles by means of the photophoretic effect, particles which would otherwise impinge upon and contaminate the substrate surface.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. An apparatus for processing a substrate surface of a substrate, comprising: a process chamber;   means for processing the substrate surface by chemically or physically altering the substrate surface;   a substrate fixture for holding the substrate in the processing chamber so that the substrate surface is exposed to the inside of the processing chamber;   means for inhibiting contamination of the substrate surface by particles, comprising: (a) means for forming a first laser beam;   (b) means for forming a second laser beam;   (c) means for scanning the first laser beam along first scanning trajectories which do not contact the substrate surface, wherein each of the first scanning trajectories has a segment disposed closer to a point on the substrate surface than all opposing structural elements in the processing chamber which are opposed to the substrate surface;   (d) means for scanning the second laser beam along second scanning trajectories which do not contact the substrate surface, wherein each of the second scanning trajectories has a segment disposed closer to a point on the substrate surface than all opposing structural elements in the processing chamber which are opposed to the substrate surface; and     wherein at least some of the second scanning trajectories and at least some of the first scanning trajectories cross to provide a tent-like cover over the substrate surface;   wherein a vector that is collinear with any of said first scanning trajectories and which points along the direction of propagation of said first laser beam at a point that opposes the substrate surface has a vector component that is perpendicular to the substrate surface that points away from the substrate surface;   wherein a vector that is collinear with any of said second scanning trajectories and which points along the direction of propagation of said second laser beam at a point that opposes the substrate surface has a vector component which is perpendicular to the substrate surface that points away from the substrate surface.   
     
     
       2. An apparatus according to claim 1, wherein one of the first trajectories has a segment which is closer to a point on the substrate surface than all opposing structural elements inside the processing chamber which oppose the substrate surface. 
     
     
       3. An apparatus according to claim 1, further comprising a beam stop for stopping the first laser beam, the beam stop positioned in the path of the first laser beam. 
     
     
       4. An apparatus according to claim 1, wherein the means for forming the first laser beam includes a laser which is disposed outside of the processing chamber and wherein the processing chamber comprises a laser window along the trajectory of the first laser beam so that the first laser beam passes from outside of the processing chamber through the laser window and then into the processing chamber. 
     
     
       5. An apparatus according to claim 1, wherein the substrate fixture is grounded. 
     
     
       6. An apparatus according to claim 1, further comprising particle collecting means disposed in the first trajectories of the first laser beam for collecting particles captured by the first laser beam and transported by the first laser beam to the particle collection means. 
     
     
       7. An apparatus according to claim 6, wherein the particle collection means comprises a cooled surface. 
     
     
       8. An apparatus according to claim 6 wherein the particle collection means comprises: first opposed conducting plates and means for supplying an electric potential across the first opposed conducting plates.   
     
     
       9. An apparatus according to claim 8, further comprising: a laser optic surface; and   wherein the laser optic is disposed along the first trajectory for transmitting or reflecting the first laser beam; and   wherein the first opposed conducting plates are adjacent the laser transmission surface.   
     
     
       10. An apparatus according to claim 8, further comprising: a laser optic surface in the processing chamber that is disposed along the first trajectories of the first laser beam for either transmitting or reflecting the laser beam; and   wherein the first opposed conducting plates are adjacent the laser optic surface.   
     
     
       11. An apparatus according to claim 6, wherein the particle collection means comprises: a cooled surface, first opposed conducting plates, and means for supplying an electric potential across the first opposed conducting plates.   
     
     
       12. An apparatus according to claim 1, wherein said first laser beam is focused at a point in said processing chamber. 
     
     
       13. An apparatus according to claim 1, wherein said means for scanning the first laser beam provides a scanning rate at a high enough frequency so that all particles whose trajectories intersect a path of the scanned beam experience a photophoretic force due to the first laser beam. 
     
     
       14. An apparatus for processing a substrate surface of a substrate, comprising:. a process chamber;   means for processing the substrate surface by chemically or physically altering the substrate surface;   a substrate fixture for holding the substrate in the processing chamber so that the substrate surface is exposed to the inside of the processing chamber;   means for inhibiting contamination of the substrate surface by particles, comprising: (a) means for forming a first laser beam,   (b) means for forming a second laser beam;   (c) means for fanning out the first laser beam into a first fan shaped laser beam along a first trajectory which does not contact the substrate surface;   (d) means for fanning out the second laser beam into a second fan shaped laser beam along a second trajectory which does not contact the substrate surface;     wherein the first fan shaped laser beam and the second fan shaped laser beam cross inside the processing chamber to provide a tent-like cover over the substrate surface such that a vector pointing along any direction of propagation of either the first fan shaped laser beam or the second fan shaped laser beam at a point that opposes the substrate surface has a vector component in a direction that is perpendicular to the substrate surface that points away from the substrate surface.   
     
     
       15. An apparatus according to claim 14, wherein the first trajectory has a segment which is closer to a point on the substrate surface than all opposing structural elements inside the processing chamber which oppose the substrate surface. 
     
     
       16. An apparatus according to claim 14, further comprising a beam stop for stopping the first laser beam, the beam stop being positioned in the path of the first laser beam. 
     
     
       17. An apparatus according to claim 14, wherein the means for forming the first laser beam includes a laser that is disposed outside of the processing chamber and wherein the processing chamber comprises a laser window along the laser beam trajectory so that the first laser beam passes from outside of the processing chamber through the laser window and then into the processing chamber. 
     
     
       18. An apparatus according to claim 14, wherein the substrate fixture is grounded. 
     
     
       19. An apparatus according to claim 14, further comprising particle collection means disposed in the first trajectory of the first laser beam for collecting particles captured by the first laser beam and transported by the first laser beam to the particle collection means. 
     
     
       20. An apparatus according to claim 19, wherein the particle collection means comprises a cooled surface. 
     
     
       21. An apparatus according to claim 19, wherein the particle collection means comprises: first opposed conducting plates; and   means for supplying an electric potential across the first opposed conducting plates.   
     
     
       22. An apparatus according to claim 19, wherein the particle collection means comprises: a cooled surface;   a first set of opposed conducting plates; and   means for supplying an electric potential across the first set of opposed conducting plates.   
     
     
       23. An apparatus according to claim 14, wherein said first laser beam is focused at a point in said processing chamber. 
     
     
       24. An apparatus according to claim 14, wherein the first and second laser beams have a cone-like structure.